by Ernest Thompson Seton

The spacing can best be done by actually registering the course of the sun's shadow during the entire day, making
sure that the pointer is constantly pointed to the north.

More scientific ways of ascertaining the angles between the lines may be used
if desired; for instance, such as are given on page 81 of Professor Jacoby's Astronomy
or in the Encyclopedia Britannica.

However, there is no necessity for those living in the latitude of New York City to
use any of the above methods, as the following angles have been worked out and
tested and will be found to be approximately correct:

Between Hr.

12 Noon and Hrs.

1 or 11

10 degrees

" Hrs.

1 & 2 "

11 & 10

11

"
"

2 & 3 "

10 & 9

12 1/2

"
"

3 & 4 "

9 & 8

15

"
"

4 & 5 "

8 & 7

19

"
"

5 & 6 "

7 & 6

22 1/2

Total from 12 to 6 (1/4 the
circle)

90 degrees

The angle between hrs. 6 and 7 P. M. (likewise between 5 and 6 A.M.) is also
22 1/2 degrees, as the night hour-lines are prolongations of the day hour-lines.

For boys and girls who might have difficulty in determining angles by
degrees, the following thumb rule for the locality of New York City will be
found useful:

Have the quarter circle from 12 to 6 o'clock divided into six unequal parts,
the smallest sector being next to 12 o'clock and the other sectors uniformly
increasing in size so that the largest is next to 6 o'clock. The smallest angle
should be 1/9 of the quarter circle, and the largest angle should be about 1/4
the quarter circle.

Bear in mind that the entire dial must be symmetrical in two ways; that is,
the A. M. and P. M. halves of the dial are symmetrical, also the day-time and
night-time halves are symmetrical (insofar as the sun shores before 6 A. M. and
after 6 P. M.). This double symmetry is true in any latitude or longitude; hence
the importance of affixing the pointer at the center of the dial, its upper edge
meeting the surface of the dial on the straight line extending across from 6 A.
M. to 6 P. M.

When the dial has been constructed by any of the above methods, put it in the
sun and do not be surprised if it does not register the same time as common
clock time. It will probably be a few minutes ahead or behind it even if
accurately made, as for astronomical reasons too complex for explanation here
the sun is irregular in its apparent movements. To ascertain our railroad time
there would have to be convenient to hand the following memorandum:

A further allowance would have to be made if the location does not happen to
be on the standard meridian from which clock or railroad time is taken. For
instance, New York City lies one degree east of the standard meridian for Eastern
time, hence a further adjustment would have to be made due to the fact that the
sun is thus 4 minutes faster than it would be on the exact meridian. The
variation of any other locality can be calculated similarly, allowing 4 minutes
fast for each degree the place lies east of its standard meridian; similarly the
dial will be slow if its locality is west of its meridian.

If the hour-lines are originally laid out on the dial by the practical
process of noting the movement of the sun's shadow hour by hour, then it is
preferable either that this be done at one of the times during the year when
sun-time and clock time are approximately identical or that proper allowance computed from the above table be made; otherwise it is easy
to see that a
variation from clock time rising at times to a maximum of half an hour might
result.

Another point which is added for the sake of completeness rather than its
importance, is the variation between morning and afternoon time caused by the width of the sun
itself, as it covers
half a degree in the sky. The light from preceding edge of the sun is in the
morning a minute ahead of what it would be were the sun but a point in the sky. Likewise
the light lags a minute behind in the afternoon. These trivial variations can of
course be disregarded.

Caution: Do not attempt to locate the north by following rally a magnetic
needle. In New York City the needle points ten degrees to the west of the real
north. Moreover, a compass is apt to be affected by surrounding iron or steel
objects
such as a steam radiator. The north pole is a much more accurate guide although it
at times varies a degree from the true north. For the information of those living
in New York City it is convenient to know that the up and down avenues of the city
(such as Fifth Avenue and Amsterdam Avenue) point east of north at an angle of about 30
degrees.

It is better to
have the pointer as thin as possible, as if has any substantial thickness the eastern and western
halves of the dial markings will have to be separated by that width. This is
because the sun registers with one edge in the morning and the other edge in the
afternoon. Also do not forget that it is always the side of the shadow cast by
the upper side of the pointer which is to be regarded in noting the time.

Sun dials are an ornament to any garden. New York residents can find one
quietly at work in the flower gardens at Van Cortlandt Park. Chronic pessimists
would do well to ponder the inscription on King Edward's sun dial:

"Let others tell of rains and showers,
I only record the sunny
hours."

CLARKE G. DAILEY.

To make a more scientifically accurate Sundial, see Collins Book of the
Stars.

Search This Site:

Search Amazon.Com:

When you place an order
with Amazon.Com using
the search box below, a small referral fee is returned to The Inquiry Net to
help defer the expense of keeping us online. Thank you for your
consideration!

Old School Scouting:
What to Do, and How to Do It!

To Email me, replace "(at)" below with
"@"Rick(at)Kudu.Net

If you have questions about one of my 2,000 pages here, you must send me the
"URL" of the page! This "URL" is sometimes called the
"Address" and it is usually found in a little box near the top of your
screen. Most
URLs start with the letters "http://"

The purpose of this Website is to provide access
to hard to find, out-of-print documents. Much of the
content has been edited to be of practical use in today's world and is not
intended as historical preservation. I will be happy to provide
scans of specific short passages in the original documents for people involved in
academic research.